Methods in which structures that are located at a depth (Z direction) below the surface of an examined object are imaged by means of ultrasound signals in a measurement zone are applied for a range of applications, for example, in materials testing and product testing and in medicine. A typical example of this is sonography. This is, by nature, a method for section imaging (ultrasound tomography). A section image of the sonogram with conventional ultrasound probes shows a sectional view of an object under examination, for example, in a material or in a bodily tissue. In doing so, differences in the acoustical (reflection) characteristics in the interior of the object under examination (ultrasound signals) are visualized. In the two-dimensional section image generated in this way, a first dimension extends along a crystal array of the ultrasound head (X direction). The second dimension reflects the distribution of the acoustical characteristics in depth (Z direction). Therefore, the measurement zone examined in this way preferably extends in an X-Z plane and has only a slight thickness in Y direction.
In contrast, in methods based on the detection of radiation signals of radionuclides, two-dimensional images are acquired through which a two-dimensional distribution of radiation signals and their intensities is imaged in an X-Y plane. It is not possible to directly correlate the two-dimensional distribution with a depth localization of locations of origin of the radiation signals in an individual image.
Conventional gamma probes deliver information only as number and/or acoustical signal (whistle, clicking sound) so that no information about the depth location of a storage lesion is obtained. These probes use an individual gamma detector and a passive metal collimator of high density to define the visual field of the detector and to suppress background radiation from the environment in that this background radiation does not reach the detector and is not detected by it. With high power, the collimators are large and heavy.
Apparatus is known in which an ultrasound probe and at least one radiation detector are arranged in proximity to one another or in a common measuring head.
A solution of this kind is known from U.S. Pat. No. 7,094,203 B2. In a housing, a collimator is arranged upstream of a quantity of radiation detectors (array), and a detection zone of the radiation detectors is directed and limited through the action of the collimator. Directly adjacent to the housing, an ultrasound probe is arranged in a common measuring head. Ultrasound signals are detected in a common measurement zone by the ultrasound probe in an X-Z plane. The array of radiation detectors is swivelably arranged so that a measurement zone of the array can be directed through the measurement zone of the ultrasound probe. By means of a swiveling movement of the array, a point of intersection of the two measurement zones can be displaced as a focal plane along the measurement zone of the ultrasound probe and various measurement positions of the radiation detectors can be adjusted with respect to the common measurement zone. The information about depth localization of locations of origin can be obtained by reconstructing the individual focal planes.
A similar method is described in EP 1 284 655 B1. In this case, a quantity of radiation detectors is arranged so as to be directed at various angles into a measurement zone, and the detection zones of the radiation detectors intersect in a focus line in the measurement zone. For the alignment of the detection zones of the radiation detectors which is critical for this purpose, a collimator is arranged upstream of each radiation detector. The respective angles of the radiation detectors are known. By making use of the knowledge of the respective currently adjusted angles, the position of a current focus line can be determined. If the focus line is guided through the measurement zone and, in so doing, the detected radiation signals are stored such that they are associated with the respective focus line, an imaging of the radionuclide distribution, i.e., the locations of origin, can be reconstructed. In addition, an ultrasound image of the measurement zone is captured. The data from the ultrasound tomogram and the reconstruction of the distribution of the locations of origin in the common measurement zone can subsequently be imaged in a hybrid image.
A measuring head in which an ultrasound probe is arranged next to or in an array of radiation detectors is known from US2013/0172739A1. Detection of ultrasound signals and radiation signals is only possible in a directed manner. The three-dimensional distribution of the locations of origin is only possible through detection of corresponding measurement values from different measurement positions of the measuring head and through reconstruction of the measurement values detected at the various measurement positions.
All of the solutions of the prior art require a reconstruction of data in order to image a distribution of the locations of origin and ultrasound images based on radiation signals and ultrasound signals. A definitive spatial association of increased nuclide-storing findings with the sonogram is only possible at high computational expenditure and with a very high risk and unpredictability of spatial offsets caused by the calculation algorithms. Therefore, it would be desirable to provide an integrated probe for generating anatomically correctly matching section images (identical imaging planes) simultaneously as far as possible from tissue echogenicity (ultrasound signals) and radionuclide distribution. There is no satisfactory state-of-the-art solution at the present time.